Vessels or drums are often used to store and dispense substances such as gas or liquid. An opening is provided in the vessel to allow these substances to be filled into and dispensed from the vessel. The vessel is sealed at its opening with a removable bung or cap to prevent its contents from escaping from the opening.
The vessels are sometimes pressurized to facilitate the dispensing of stored liquids or gases or as the result of thermal expansion. However, the pressure increases the risk of leakage from the vessel opening. The leakage may be caused by the flexing and/or distortion of the vessel structure caused by the internal pressure, as well as by temperature changes and shipment activity. This problem is particularly troublesome when the vessel or the bung are made with plastic materials.
In the past, attempts have been made to design a pressure vessel and bung to provide an adequate seal. Sealing materials or gaskets have been used with bungs to improve the leak resistance of the seal between the bung and the vessel opening. An axial compression force is applied to the gasket by the bung, urging it against the wall of the vessel adjacent the opening.
However, the pressurized liquid or gas in the vessel exerts radial outward forces on the gasket material. These outward forces may result in the forcing of the gasket radially outwardly and create a leak or a total rupture of the gasket.